Laurel Wilt, caused by Raffaelea lauricola


A new disease first appeared on redbay, Persea borbonia, in the Savannah, Georgia area in 2003 and is established on the Atlantic coastal plains of South Carolina, Georgia and Florida. Native members of the Lauraceae are affected, as is avocado (P. americana). Our work with Steve Fraedrich established that the causal agent is a newly-described ambrosia beetle symbiont, Raffaelea lauricola, and the introduced Xyleborus glabratus is the main vector. The appearance of the disease was coincidental with the appearance of the Asian redbay ambrosia beetle, and the pathogen was probably brought over with the ambrosia beetle in solid wood packing material from Asia. Unfortunately, there is no attempt to contain the spread of the pathogen and vector.

You can download PDFs of four research publications I have on the disease and new pathogen and a recovery plan written by Bud Mayfield and others:

Fraedrich, S.W., Harrington, T.C., Rabaglia, R.J., Ulyshen, M.D., Mayfield A.E. III, Hanula, J.L, Eickwort, J.M. and Miller, D.R. 2008. A fungal symbiont of the redbay ambrosia beetle causes a lethal wilt in redbay and other Lauraceae in the southeastern United States. Plant Disease 92: 215-224 (pdf of manuscript).

Harrington, T.C., Fraedrich, S.W., and Aghayeva, D.N. 2008. Raffaelea lauricola, a new ambrosia beetle symbiont and pathogen on the Lauraceae. Mycotaxon 104: 399-404 (pdf of manuscript).

Mayfield, A. E, T. C. Harrington, S. Fraedrich, J. Hanula, and others. 2009. Recovery plan for laurel wilt on redbay. In: Plant Diseases that Threaten U.S. Agriculture. Prepared for the National Plant Disease Recovery System, USDA and the American Phytopathological Society. 27 pp. (pdf of report).

Ploetz, R., T. C. Harrington and many others. 2011. Recovery plan for laurel wilt on avocado. In: Plant Diseases that Threaten U.S. Agriculture. Prepared for the National Plant Disease Recovery System, USDA and the American Phytopathological Society. 24 pp. (pdf of report).

Harrington, T. C., D. N. Aghayeva, and S. W. Fraedrich. 2010. New combinations in Raffaelea, Ambrosiella, and Hyalorhinocladiella, and four new species from the redbay ambrosia beetle, Xyleborus glabratus. Mycotaxon 111:337-361.

Harrington, T. C., and S. W. Fraedrich. 2010. Quantification of propagules of the laurel wilt fungus and other mycangial fungi from the redbay ambrosia beetle, Xyleborus glabratus. Phytopathology 100:1118-1123.

Riggins, J. J., S. W. Fraedrich, and T. C. Harrington. 2011. First report of laurel wilt caused by Raffaelea lauricola in sassafras in Mississippi. Plant Dis. 95:1479.

Fraedrich, S.W., T. C. Harrington, C. A. Bates, J. Johnson, L. S. Reid, G. S. Best, T. D. Leininger, and T. S. Hawkins. 2011. Susceptibility to laurel wilt and disease incidence in two rare plant species, pondberry and pondspice. Plant Dis. 95:1056-1062.

Harrington, T. C. , H. Y. Yun, S. S. Lu, H. Goto, D. N. Aghayeva, and S. W. Fraedrich. 2011. Isolations from the redbay ambrosia beetle, Xyleborus glabratus, confirm that the laurel wilt pathogen, Raffaelea lauricola, originated in Asia. Mycologia 103:1028-1036.


The Laurel Wilt Task Force was formed to help coordinate research, outreach, and monitoring efforts. The task force and the US Forest Service has all the reference material you need on the disease at the Laurel Wilt Webpages.

 

Young redbay sapling killed by Raffaelea lauricola. Red bay is usually an understory species.

 

Base of a diseased redbay, where females of Xyleborus glabratus (smaller holes) and Xylosandrus crassiusculus (larger holes) have initiated their galleries. The discoloration above and below the attacks are a host response due to the wounding and colonization by the respective fungal symbionts.

 

Twig of a healthy redbay that has recently been attacked by females of Xyleborus glabratus. Where populations of the beetle are high, such aborted galleries are common in small diameter twigs and branches. Raffaelea lauricola, which grows in the mycangium of the beetle, may become established in these aborted galleries and systemically colonize the tree and cause wilt.

 

Black sapwood discoloration following the annual rings is indicative of laurel wilt, a typical vascular wilt disease. Ambrosia beetle galleries are seen in the upper right of the photo. Brood of X. glabratus feed on R. lauricola and other Raffaelea species that sporulate in the galleries. Young adult females of X. glabrautus acquire the Raffaelea species in their mycangia, and the fungi grow in a yeast phase inside the mycangium.


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